Chrysler Repair: update on 89 3.0L running poorly when warm, failure code, oxygen sensor

Question
Hi Roland,hey thanks for the help so far just thought i would tell you that a guy I spoke to today said that it could be the fuel pump getting hot and stopping is that possible? how about the coil could that be the problem or even the SEMC itself? there are still no codes displayed I am thinking about putting a muffler in the center of the exhaust where the cat was do you think that might help? By the way it was running really bad when it was cold today and a quick reset of the ignition put it right again . Thank you in advance -Paul oh and to answer your question , yes I am on the UK car category now thanks .

Answer
Hi Paul,
If it were the coil you would sense that as missing, if it were the fuel pump it would be leaning out, if it were the SMEC you might think there would be a 62 or 63 code though there is not a frank failure code for the module. The fact that you get codes, and a 55 that makes sense leaves me doubtful it is the SMEC. You could check the fuel pressure too when it is acting up. If it seems to be a mixture issue (too rich would certainly make me suspect the MAP).
I doubt the exhaust would be the problem it the leaks are fairly far from the oxygen sensor. However, leaks near that sensor would certainly be a possible cause.
I wish I had something definitive.
I have a DRB II which I would lend you if you would like, and you would cover the shipping both ways.
Roland